Staff at Dublin, Cork and Shannon airports have balloted overwhelmingly to take industrial action over a plan by Aer Lingus to cease providing them with cheap flights.
There is no immediate threat of disruption, however, and talks on the issue between the airline and the Dublin Airport Authority are to begin next week.
The authority, which remains in formal charge of all three airports, is hoping to persuade Aer Lingus to reverse the decision.
It also said yesterday it was "willing to explore alternative solutions", in the event of Aer Lingus proceeding with its plan to drop the flight concessions.
It is understood these include the possibility of arranging similar concessions with another airline, or paying workers a lump sum in return for dropping the scheme.
Members of four unions - SIPTU, the TEEU, IMPACT and Mandate - have balloted to strike in response to the threat to withdraw the concession. They will meet on Monday to decide their next move.
The unions said yesterday the staff had been guaranteed that workers' terms and conditions would not be diminished following the break-up of Aer Rianta into three separate airport management companies.
"The ink is hardly dry on the State Airports Act and it seems the new [Dublin Airport] Authority is reneging on those commitments," said Mr Ian McDonnell of the TEEU.
The issue is complicated, however, by the fact that the concessions are provided by Aer Lingus rather than the workers' employer, the Dublin Airport Authority.
It said in a statement yesterday it was "disappointed" to learn of the Aer Lingus decision and was "actively engaged" with the airline to try to have it reversed.
"In this context, Aer Lingus has agreed to extend its deadline for cessation of the service until the end of February," it said.
Aer Lingus said in a statement that the discount scheme involved significant administration costs and it had to drive costs down in order to lower fares.
It would meet the Dublin Airport Authority next Friday to begin discussions, which would conclude by the end of February.
It is understood the three airports currently pay Aer Lingus about €300,000 a year for the concession, which allows 1,400 staff to access cheap flights on a standby basis. There is a 1,000-strong waiting list among other airport staff, who qualify on a seniority basis as existing members leave the scheme.
